1. Field of the Invention
The present invention relates to a zoom lens and more particularly to a zoom lens suitable for a video camera, etc.
2. Related Background Art
Conventionally, all zoom lenses for video cameras are formed of a uniform medium lens, and many of those are formed of four lens groups having positive, negative, negative and positive refracting powers or positive, negative, positive and positive refracting power from the object side in that order.
In those zoom lenses having four lens groups, the second lens group and the third lens group or the second lens group and the fourth lens group are shifted along the optical axis in a zooming operation (changing a focal length).
Recently, there have been strong demands for small, lightweight and high performance zoom lenses. In general, as a method of forming small and lightweight zoom lenses, respective powers (refracting powers) of lens groups are made strong.
However, in the conventional zoom lenses formed of the wholly uniform medium lens, as the result of making them small and lightweight, corrections of various aberrations are sacrificed, causing deterioration of imaging performance.